Catalytic combustor for substantially eliminating nitrous oxide emissions

ABSTRACT

A combustor for a gas powered turbine which employs a heat exchanger and a catalyst to combust a fuel without the emission of undesired chemical species. A gas powered turbine requires expanding gases to power the turbine blades. Fuel is combusted to produce the required gases. A catalyst is employed to lower the combustion temperature of the fuel. The catalyst is placed on a set of tubes in the heat exchanger such that a portion of the thermal energy may be transferred to the air before it engages the catalyst. After encountering the catalyst, the combusted fuel increases the temperature of the air to an auto-ignition temperature so that no other ignition source is needed to combust additional fuel.

FIELD OF THE INVENTION

[0001] The present invention relates generally to gas powered turbines for generating power, and more particularly to a low nitrous oxide emission combustion system for gas powered turbine systems.

BACKGROUND OF THE INVENTION

[0002] It is generally known in the art to power turbines with gases being expelled from combustion chambers. These gas powered turbines can produce power for many applications such as terrestrial power plants. In the gas powered turbine a fuel, such as a hydrocarbon (for example methane or kerosene) or hydrogen, is combusted in an oxygen rich environment. Generally, these combustion systems have high emissions of undesirable compounds such as nitrous oxide compounds (NOX) and carbon containing compounds. It is generally desirable to decrease these emissions as much as possible so that undesirable compounds do not enter the atmosphere. In particular, it has become desirable to reduce NOX emissions to a substantially low amount. Emissions of NOX are generally desired to be non-existant, and are accepted to be non-existent, if they are equal to or less than about one part per million volume of dry weight emissions.

[0003] In a combustion chamber fuel, such as methane, is combusted in atmospheric air where temperatures generally exceed about 2600° F. (about 1427° C.). When temperatures are above 2600° F., the nitrogen and oxygen compounds, both present in atmospheric air, undergo chemical reactions which produce nitrous oxide compounds. The energy provided by the high temperatures allows the breakdown of dinitrogen and dioxygen, especially in the presence of other materials such as metals, to produce NOX compounds such as NO₂ and NO.

[0004] It has been attempted to reduce NOX compounds by initially heating the air before it enters the combustion chambers to an auto-ignition temperature. If the air enters the combustion chamber at an auto-ignition temperature, then no flame is necessary to combust the fuel. If no flame is required in the combustion chamber, the combustion chamber temperature is lower, at least locally, and decreases NOX emissions. One such method is to entrain the fuel in the air before it reaches the combustion chamber. This vitiated air, that is air which includes the fuel, is then ignited in a pre-burner to raise the temperature of the air before it reaches the main combustion chamber. This decreases NOX emissions substantially. Nevertheless, NOX emissions still exist due to the initial pre-burning. Therefore, it is desirable to decrease or eliminate this pre-burning, thereby substantially eliminating all NOX emissions.

[0005] Other attempts to lower NOX emissions include placing catalysts in catalytic converters on the emission side of the turbines. This converts the NOX compounds into more desirable compounds such as dinitrogen and dioxygen. These emission side converters, however, are not one hundred percent efficient thereby still allowing NOX emissions to enter the atmosphere. The emission converters also use ammonia NH₃, gas to cause the reduction of NOX to N₂. Some of this ammonia is discharged into the atmosphere. Also, these converters are expensive and increase the complexity of the turbine and power production systems. Therefore, it is also desirable to eliminate the need for emission side catalytic converters.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a combustor for a gas powered turbine which employs a heat exchanger and a catalyst to combust a fuel without the emission of undesired chemical species. A gas powered turbine requires expanding gases to power the turbine fans or blades. Fuel is generally combusted to produce the required gases. A catalyst is employed to lower the combustion temperature of the fuel. The catalyst is placed on a set of tubes in a heat exchanger such that a portion of the thermal energy may be transferred to the air before it engages the catalyst. After encountering the catalyst, the fuel that was combusted increases the temperature of the air to an auto-ignition temperature so that no other ignition source is needed to combust additional fuel.

[0007] A first preferred embodiment of the present invention comprises a combustion system for use in a turbine which combusts a fuel in the presence of air, which substantially eliminates nitrous oxide emissions. The combustion system comprises a heat exchanger. The heat exchanger includes at least one catalyst tube extending along a first axis and at least one cooling tube extending along a second axis. The axes of the catalyst tube and the cooling tube are generally parallel. The catalyst tube is in thermal contact with the said cooling tube. The air is adapted to first flow through the cooling tube and then through the catalyst tube. A catalyst is placed inside the catalyst tube. The catalyst is adapted to combust the fuel with the air. The air is adapted to flow past the catalyst tube and through the cooling tube, wherein the air receives thermal energy from the catalyst tube as the air flows through the cooling tube and past the catalyst tube.

[0008] A second preferred embodiment includes a turbine system comprising a compressor adapted to produce compressed atmospheric air; a combustion system for mixing and combusting a fuel in the compressed atmospheric air to produce expanding gases; and a turbine which is powered by the expanding gases. The combustion system comprises a first fuel supply to supply fuel to the compressed atmospheric air. The combustion system also includes a heat exchanger comprising at least one catalyst tube comprising a catalyst coated on the inside of the catalyst tube, wherein the compressed air and the fuel flow through the catalyst tube. A second fuel supply supplies fuel to the compressed atmospheric air after the compressed atmospheric air has passed through the catalyst tube.

[0009] A preferred method of operating the present invention includes combusting a fuel in the presence of atmospheric air while substantially eliminating the emission of nitrous oxide compounds. The method comprises providing a heat exchanger comprising hollow tubes; placing a catalyst on at least a portion of the interior of the hollow tubes; forming a first fuel-air mixture by mixing a first portion of the fuel and the air; producing a auto-ignition air stream by combusting the first fuel-air mixture by contacting the first fuel-air mixture with the catalyst; and heating the air by transferring a portion of the thermal energy from the hollow tubes to the air. Additional fuel may be combusted in the auto-ignition air stream without the application of an external igniter.

[0010] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0012]FIG. 1 is a partial cross-sectional perspective view of a gas powered turbine including a combustor according to the present invention;

[0013]FIG. 2 is a partial cross-sectional perspective view of a single combustor according to the present invention;

[0014]FIG. 3 is a detailed, partial cross-sectional, perspective view of a portion of the heat exchanger according to the present invention; and

[0015]FIG. 4 is a simplified diagrammatic view of the flow of air through the combustion chamber according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0017] A gas powered combustion turbine 10 may use several different gaseous fuels, such as hydrocarbons (including methane and propane) and hydrogen, which are combusted and expand to move portions of the gas powered turbine 10 to produce power. An important component of a gas powered turbine 10 is a compressor 12 which forces atmospheric air into the gas powered turbine 10. Also, the gas powered turbine 10 includes several combustion chambers 14 for combusting fuel. The combusted fuel is used to drive a turbine 15 including turbine blades or fans 16 which are axially displaced in the turbine 15. There are generally a plurality of turbine fans 16, however, the actual number depends upon the power the gas powered turbine 10 is to produce. Only a single turbine fan is illustrated for clarity. In general, the gas powered turbine 10 ingests atmospheric air, combusts a fuel in it, and powers the turbine fans 16. Essentially, air is pulled in and compressed with the compressor 12, which generally includes a plurality of concentric fans which grow progressively smaller along the axial length of the compressor 12. The fans in the compressor 12 are all powered by a single axle. The high pressure air then enters the combustion chambers 14 where fuel is added and combusted. Once the fuel is combusted, it expands out of the combustion chamber 14 and engages the turbine fans 16 which, due to aerodynamic and hydrodynamic forces, spins the turbine fans 16. The gases form an annulus which spin the turbine fans 16, which are in turn affixed to a shaft (not shown). Generally, there are at least two turbine fans 16. One or more of the turbine fans 16 engage the same shaft that the compressor 12 engages. The gas powered turbine 10 is self-powered since the spinning of the turbine fans 16 also powers the compressor 12 to compress air for introduction into the combustion chambers 14. Other turbine fans 16 are affixed to a second shaft 17 which extends from the gas powered turbine 10 to power an external device. It will be understood that the gas powered turbines are used for many different applications such as engines for vehicles and aircraft or for power production in a terrestrially based gas powered turbine 10. After the gases have expanded through the turbine fans 16, they are expelled out the exhaust portion which includes an exhaust port 18.

[0018] The gases which are exhausted from a gas powered turbine 10 include many different chemical compounds that are created during the combustion of the atmospheric air in the combustion chambers 14. If only pure oxygen and pure hydrocarbon fuel, were combusted, absolutely completely and stoichiometrically, then the exhaust gases would include only carbon dioxide and water. Atmospheric air, however, is not 100% pure oxygen and includes many other compounds such as nitrogen and other trace compounds. Therefore, in the high energy environment of the combustion chambers 14, many different compounds may be produced. All of these compounds exit the exhaust port 18. It is generally known in the art that an equivalence ratio is determined by dividing the actual ratio of fuel and air by a stoichiametric ratio of fuel to air (where there is not an excess of one starting material). Therefore, a completely efficient combustion of pure fuel and oxygen air would equal an equivalence ratio of one.

[0019] It will be understood that the gas powered turbine 10 may include more than one combustion chamber 14. Any reference to only one combustion chamber 14, herein, is for clarity of the following discussion alone. According to a preferred embodiment of the present invention, the combustor chamber 14 includes a premix section or area 30, a heat exchange or pre-burn section 32, generally enclosed in a heat exchange chamber 33, and a main combustion section 34. A first or premix fuel line 36 provides fuel to the premix area 30 through a fuel manifold 37 while a second or main fuel line 38 provides fuel to the main combustion section 34. Positioned in the premix area 30 is a premix injector 40 which injects fuel from the first fuel line 36 into a premix chamber 42. Air from the compressor 12 enters the premix area 30 through cooling tubes 44 of a heat exchanger 45 (detailed in FIG. 3). The premix chamber 42 encompasses a volume between the premix injector 40 and the exit of the cooling tubes 44.

[0020] With further reference to FIG. 2, a plurality of catalytic heat exchange or catalyst tubes 48 extend into the heat exchange area 32. The heat exchange tubes 48 are spaced laterally apart. The heat exchange tubes 48, however, are not spaced vertically apart. This configuration creates a plurality of columns 49 formed by the heat exchange tubes 48. Each heat exchange tube 48, and the column 49 as a whole, define a pathway for air to travel through. The columns 49 define a plurality of channels 50. Extending inwardly from the walls of the heat exchange chamber 33 are directing fins (not particularly shown). The directing fins direct the flow of air to the top and the bottom of the heat exchange chamber 33 so that air is directed to flow vertically through the channels 50 defined by the heat exchange tubes 48.

[0021] Near the ends of the heat exchange tubes 48, where the heat exchange tubes 48 meet the main combustion section 34, is a main injector 52. The second fuel line 38 provides fuel to the main injector 52 so that fuel may be injected at the end of each heat exchange tube 48. Spaced away from the main injector 52, towards the premix area 30, is an intra-propellant plate 54. The intra-propellant plate 54 separates the air that is traveling through the channels 50 and the fuel that is being fed to the fuel manifold region between the main injector face 52 and intra-propellant plate 54. It will be understood, that the intra-propellant plate 54 is effectively a solid plate, though not literally so in this embodiment. The placement of the heat exchange tubes 48 dictate that the intra-propellant plate 54 be segmented. Air which exits out the heat exchange tubes 48 is entrained with fuel injected from the main injector 52 and this fuel then combusts in the main combustion section 34. The main combustion section 34 directs the expanding gases of the combusted fuel to engage the turbine fans 16 so that the expanded gases may power the turbine fans 16.

[0022] Turning reference to FIG. 3, an enlarged portion of the heat exchanger 45 including a catalyst is shown. Although the heat exchanger 45 includes a large plurality of tubes, as generally shown in FIG. 2, only a few of the heat exchange tubes 48 and cooling tubes 44 are illustrated for greater clarity. The heat exchanger 45 is similar to that described in U.S. Pat. No. 5,309,637 entitled “Method of Manufacturing A Micro-Passage Plate Fin Heat Exchanger” to Michael P. Moriarty and is incorporated herein by reference. The heat exchanger 45 includes a plurality of cooling tubes 44 disposed parallel to and closely adjacent the heat exchange tubes 48. Each of the cooling tubes 44 and the heat exchange tubes 48 have a generally rectangular cross section and can be made of any generally good thermally conductive material. Preferably, the heat exchange tubes 48 and the cooling tubes 44 are formed out of stainless steel. Both the cooling tubes 44 and the heat exchange tubes 48 may be of any appropriate size, but preferably each are square having a width and height of between about 0.04 inches and about 1.0 inches (between about 0.1 centimeters and about 2.5 centimeters). The thickness of the walls of the cooling tubes 44 and the heat exchange tubes 48 may be any appropriate thickness. The walls need to be strong enough to resist the pressure of the fluids flowing through them, but still allow for an efficient transfer of heat between the inside of the heat exchange tubes 48 and the air in the channels 50 and cooling tubes 44.

[0023] The cooling tubes 44 are preferably brazed to the heat exchange tubes 48. Preferred brazing materials are those with melting temperatures above about 1000° F. (about 538° C.). It will be appreciated that while the cooling tubes 44 and the heat exchange tubes 48 are shown as being substantially square, the cross-sectional shape of the components could comprise a variety of shapes other than squares. It is believed, however, that the generally square shape will provide the best thermal transfer between the tubes 44 and 48.

[0024] The cooling tubes 44 extend parallel to the heat exchange tubes 48 for a portion of the length of the heat exchange tubes 48. The cooling tubes 44 extend between the columns 49 of the heat exchanger tubes 48. The cooling tubes 44 and the heat exchange tubes 48, when brazed together, form the heat exchanger 45 which can provide a surface-to-surface exchange of heat. It will be understood, however, that air traveling in the channels 50 between the heat exchange tubes 48 will also become heated due to the heat transferred from the heat exchange tubes 48 to the air in the channels 50.

[0025] Referring further to FIG. 3, fuel injector ports 60 are formed in the main injector 52. The injector ports 60 may be provided in any appropriate number, however, preferably there is approximately one injector port 60 for each heat exchange tube 48. Therefore, as air exits the heat exchange tube 48, fuel is injected from the injector port 60 to the stream of air emitted from each heat exchange tube 48. In this way, the fuel can be very efficiently and quickly distributed throughout the air flowing out of the heat exchanger 45.

[0026] On the interior walls of each heat exchange tube 48 is a coating of a catalyst. The catalyst may be any appropriate catalyst to combust a hydrocarbon fuel, but preferably includes a mixture of platinum and palladium. The catalyst is able to combust a hydrocarbon fuel, such as methane, without the presence of a flame or any other ignition source. The catalyst is also able to combust the fuel without generally involving any side reactions. Therefore, the combustion of fuel does not produce undesired products.

[0027] With continuing reference to FIGS. 1-3 and further reference to FIG. 4, the method of using the combustion chamber 14 according to the present invention will be described. The air follows the circuit indicated by the arrows in FIG. 4. It will also be understood that a plurality of tubes, as described above, are present in the heat exchanger, but have been removed for clarity in the present description of the air flow. Atmospheric air is compressed in the compressor 12 and then introduced into the heat exchange chamber 33 at a high pressure. The air that enters the heat exchange chamber 33 is directed by the directing fins to the top and bottom of the heat exchange chamber 33 so that the air may flow through the channels 50. The air that enters the heat exchange chamber 33 is at a temperature between about 100° F. and about 800° F. (about 370° C. and about 427° C.). Generally, however, the air enters the heat exchanger 45 at a temperature between about 120° F. and about 300° F. (about 49° C. and about 148° C.).

[0028] As the air travels in the channels 50, the air increases in temperature to become “hot” air. The hot air flows through the pathway formed by the cooling tubes 44 and into the premix area 30. The hot air also receives thermal energy while flowing through the cooling tubes 44. It will be understood that the cooling tubes 44 are adjacent a portion of the heat exchange tubes 48. The temperature of the hot air, as it enters the premix area 30, is between about 800° F. and about 1000° F. (about 427° C. and about 538° C.). The air in the premix area 30 makes a turn within the premix chamber 42. As the air turns inside the premix chamber 42, the premix injector 40 injects fuel into the air, entraining the fuel in the air. About 30% to about 60% of all the fuel used to power the gas powered turbine 10 is entrained in this manner in the premix chamber 42. The premix injector 40 injects approximately 30-60% of the fuel into the heated air as it enters the premix chamber 42.

[0029] After the air enters the premix chamber 42, it then flows out through the pathway formed by the heat exchange tubes 48. In the heat exchange tubes 48, the fuel in the hot air combusts as it engages the catalyst which has been coated on the inside walls of the heat exchange tubes 48. As the fuel combusts, the temperature of the hot air rises again to between about 1400° F. and 1700° F. between (about 760° C. and about 927° C.). The temperature of the air reached in the heat exchange tubes 48 is at least at the auto-ignition temperature of the fuel being used in the gas powered turbine 10. The auto-ignition temperature of the air is the temperature that the air must be at so that when more fuel is injected into the air the fuel ignites automatically without any other catalyst or ignition source.

[0030] Additional fuel is injected through the main injector 52 as the air exits the heat exchange tubes 48 and enters the main combustion section 34. The fuel injected from the main injector 52 is injected through the individual injector ports 60. As described above, the ratio of heat exchange tubes 48 to fuel injector ports 60 is about one. It will be understood, however, that any appropriate ratio of heat exchange tubes 48 to fuel injector ports 60 may be used. Therefore, all of the air exiting the heat exchanger 45 is thoroughly mixed with fuel. Any additional fuel to power the gas powered turbine 10 is injected at this point, such that no more fuel is added to the air at any other point in the gas powered turbine 10.

[0031] As discussed above, the air that exits the heat exchanger 45 is at the auto-ignition temperature of the fuel used in the gas powered turbine 10. Therefore, as soon as the fuel reaches the temperature of the air, the fuel ignites. Since the fuel has been thoroughly mixed with the air, using the fuel injector ports 60, the combustion of the fuel will be nearly instantaneous and will not produce any localized hot spots. Since the fuel is so well mixed with the air exiting the heat exchanger 45, there will be no one point which has more fuel than any other point, which would create hot spots in the main combustion section 34. Therefore, the temperature of the air coming off of the main injector 52 and into the main combustion section 34 will be substantially uniform. During operation of the gas powered turbine 10, quite simply the fuel's characteristic mixing time is shorter than the auto-ignition delay time.

[0032] The temperature of the air, after the additional fuel has been combusted, is between about 2400° F. and 2800° F. (about 1315° C. and about 1593° C.). Different fuel to air ratios may be used to control the temperature in the main combustion section 34. The main combustion section 34 directs the expanding gases into a transition tube (not shown) so that it will engage the turbine fans 16 in the turbine area of an appropriate cross sectional flow shape.

[0033] The use of the heat exchanger 45 raises the temperature of the air to create hot air. The hot air allows the catalyst to combust the fuel that has been entrained in the air in the premix chamber 42 without the need for any other ignition sources. The catalyst only interacts with the hydrocarbon fuel and the oxygen in the air to combust without reacting any other chemical species. Therefore, the products of the combustion in the heat exchange tubes 48 are substantially only carbon dioxide and water due to the catalyst placed therein. No significant amounts of other chemical species are produced because of the catalyst. Also, the use of the heat exchange tubes 48 with a catalyst coated therein allows the temperature of the air to reach the auto-ignition temperature of the fuel so that no additional ignition sources are necessary. Therefore, the temperature of the air does not reach a temperature where extraneous species may be easily produced, such as NOX chemicals. Due to this, the emissions of the gas powered turbine 10 of the present invention has virtually no NOX emissions. That is, that the NOX emissions of the gas powered turbine 10 according to the present invention are estimated to be generally below about 1 part per million volume dry weight.

[0034] Also, the use of the heat exchanger 45 eliminates the need for any other pre-burners to be used in the gas powered turbine 10. The heat exchanger 45 provides the thermal energy to the air so that the catalyst bed is at the proper temperature. Because of this, there are no other areas for extraneous chemical species to be produced. Additionally, the equivalence ratio of the premix area is generally between about 0.20 and 0.30, while the equivalence ratio of the main injector is between about 0.50 and about 0.60. This means that the combustion will occur as a lean mixture in both areas. Therefore, there is never an excessive amount of fuel that is not combusted. Also, the lean mixture helps to lower temperatures of the air to more easily control side reactions. It will be understood that different fuel ratios may be used to produce different temperatures. This may be necessary for different fuels.

[0035] With reference to FIG. 5, a detail portion, similar to the portion illustrated in FIG. 3, of an alternative heat exchanger 145 is illustrated. A premix chamber 142 allows air from the compressor to be mixed with a first portion of fuel. Air comes from the compressor and travels through a cooling fin 144 rather than through a plurality of cooling tubes 44, as discussed above in relation to the first embodiment. The cooling fin 144 is defined by two substantially parallel plates 144 a and 144 b. It will be understood, however, that other portions, such as a top and a bottom will be included to enclose the cooling fin 144. Additionally, a heat exchange or catalyst fin 148 is provided rather than heat exchange tubes 48, as discussed above in the first embodiment. Again, the catalyst fin 148 is defined by side, top, and bottom walls and defines a column 149. Each catalyst column 149, however, is defined by a single catalyst fin 148 rather than a plurality of catalyst tubes 48, as discussed above. The cooling fin 144 may include a plurality of cooling fins 144. Each cooling fin 144, in the plurality, defines a cooling pathway. Similarly, the heat exchange fin 148 may include a plurality of heat exchange 148 fins. Each, or the plurality of, the heat exchange fins 148 defines a heat exchange or catalyst pathway.

[0036] Channels 150 are still provided between each of the catalyst fins 148 so that air may flow from the compressor through the cooling fins 144 into the premix chamber 142. Air is then premixed with a first portion of fuel and flows back through the catalyst fins 148 to the main injector plate 152. Injection ports 160 are provided on the main injector plate 152 to inject fuel as the air exits the catalyst fin 148. Any appropriate number of injection ports 160 are provided so that the appropriate amount of fuel is mixed with the air as it exits the catalyst fins 148. An intra-propellant plate 54 is also provided.

[0037] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

What is claimed is:
 1. A combustion system for use in a turbine which combusts a fuel in the presence of air, which substantially eliminates nitrous oxide emissions, comprising: a heat exchanger including: a catalyst pathway extending along a first axis; a cooling pathway extending along a second axis; wherein said first axis and said second axis are substantially parallel; wherein said catalyst pathway is in thermal contact with said cooling pathway; wherein the air is adapted to first flow through said cooling pathway and then through said catalyst pathway; a catalyst, placed within said catalyst pathway, and adapted to combust the fuel with the air; and wherein the air is adapted to first flow past said catalyst pathway and through said cooling pathway, thereby receiving thermal energy from said catalyst pathway.
 2. The combustion system of claim 1, wherein said catalyst pathway comprises a plurality of catalyst tubes, which form a plurality of catalyst tube columns each spaced apart transversally to said first axis and which define a plurality of channels adapted for allowing the air to flow therethrough; wherein said cooling pathway comprises a plurality of cooling tubes, which form a plurality of cooling tube columns each spaced apart transversally to said second axis; and wherein said cooling tubes extend substantially adjacent said catalyst tubes along said second axis for at least a portion of the length of said catalyst tubes.
 3. The combustion system of claim 2, wherein said catalyst tubes, said cooling tubes, and said channels define a flow path for the air such that the air is able to receive thermal energy from the catalyst tubes by flowing through said channels and said cooling tubes.
 4. The combustion system of claim 1, wherein said thermal energy allows the fuel to be combusted with said catalyst.
 5. The combustion system of claim 1, wherein said catalyst comprises a mixture of palladium and platinum.
 6. The combustion system of claim 1, further comprising: a heat exchange area; a pre-mix area for mixing a first portion of the fuel with the air; a main injector area comprising at least one injector for said catalyst tubes; wherein a second portion of the fuel is mixed with the air with said main injector; and wherein said main injector is adapted to mix the second portion of fuel with the air such that the temperature throughout the area of the injector is substantially equal.
 7. The combustion system of claim 1, further comprising fins adapted to direct the flow of air around said catalyst tube.
 8. The combustion system of claim 1, wherein said cooling pathway includes a cooling fin and said catalyst pathway includes a catalyst fin.
 9. A turbine, comprising: a compressor adapted to produce compressed atmospheric air; a combustion system for mixing and combusting a fuel injected into the compressed atmospheric air to produce expanding gases; a turbine which is powered by the expanding gases: wherein said combustion system comprises: a first fuel supply to supply fuel to the compressed atmospheric air; a heat exchanger comprising a catalyst section comprising a catalyst coated on the inside of said catalyst section, wherein the compressed air and the fuel flow through said catalyst section; and a second fuel supply to supply fuel to the compressed atmospheric air after the compressed atmospheric air has passed through said catalyst section.
 10. The turbine of claim 9, wherein said catalyst section comprises a plurality of said catalyst tubes each extending along a first axis; wherein said heat exchanger further includes a plurality of cooling tubes each extending along a second axis which is parallel to said first axis; wherein said catalyst tubes are arranged to form a plurality of columns spaced transversally to said first axis and defining a plurality of channels; and wherein said cooling tubes are arranged in a plurality of columns and extend a distance along said catalyst tubes and generally perpendicular to said channels.
 11. The turbine of claim 10, wherein said catalyst tubes, said cooling tubes and said channels define a flow path for the compressed atmospheric air such that the compressed atmospheric air is adapted to receive thermal energy from said catalyst tubes by flowing through said channels and said cooling tubes.
 12. The turbine of claim 10, wherein thermal energy is transferred to the compressed atmospheric air as it flows through said heat exchanger such that the fuel from the first fuel supply is combusted on said catalyst.
 13. The turbine of claim 10, further comprising: a heat exchange area; a pre-mix area for mixing a first portion of the fuel with the air; a main injector area comprising at least one injector for said catalyst tube; wherein a second portion of the fuel is mixed with the compressed atmospheric air in said main injector; and wherein said main injector is adapted to mix the second portion of fuel with the compressed atmospheric air such that the temperature throughout the area of the injector is substantially equal.
 14. The combustion system of claim 10, further comprising fins adapted to direct the flow of the compressed atmospheric air around said catalyst tube.
 15. The combustion system of claim 10, wherein said catalyst comprises a mixture of palladium and platinum.
 16. The combustion system of claim 9, wherein said catalyst section comprises a catalyst fin.
 17. For a turbine, a method of combusting a fuel in the presence of atmospheric air while substantially eliminating the emission of nitrous oxide compounds, the method comprising: providing a heat exchanger comprising a plurality of pathways; placing a catalyst on at least a portion of an interior of a number of said pathways; forming a first fuel-air mixture by mixing a first portion of the fuel and the air; producing a auto-ignition air stream by combusting the first fuel-air mixture by contacting the first fuel-air mixture with the catalyst; and heating the air by transferring a portion of thermal energy from the pathways to the air.
 18. The method of claim 17, further comprising: forming a second fuel-air mixture by adding a second portion of fuel to the auto-ignition air stream; and producing an expanding gas by combusting said second fuel-air mixture, said expanding gas occurring when the fuel in the second fuel-air mixture reaches the temperature of the auto-ignition air stream.
 19. The method of claim 18, further comprising powering a turbine with said expanding gas.
 20. The method of claim 17, wherein said first fuel-air mixture has an equivalence ratio of between about 0.10 and about 0.30.
 21. The method of claim 18, wherein said second fuel-air mixture has an equivalence ratio of between about 0.40 and about 0.60.
 22. The method of claim 17, wherein said auto-ignition air stream has a temperature between about 1400° F. and 1600° F.
 23. The method of claim 17, wherein the step of heating the air comprises transferring a portion of the thermal energy produced in the pathways when the catalyst forms the auto-ignition air stream. 